The present invention relates to a device for protecting the needle of a syringe comprising an elastic needle cap.
More precisely, this invention relates to a protection device for syringe needle of the type comprising an elastic needle cap of generally longitudinal direction presenting a closed distal end and an open proximal end, said cap being formed by a lateral wall extending from said proximal end along a proximal end zone defining an inner housing intended for receiving the distal part of the body of a needle syringe, and by an end wall whose thickness extends from said distal end along a distal end zone, said end wall being capable of being pierced over a part of its thickness by the free end of said needle, the housing comprising, from said proximal end, an opening presenting a maximum diameter, a first portion of truncated or cylindrical shape of circular cross-section, a second cylindrical portion of circular cross-section presenting a diameter smaller than the maximum diameter and intended to house the distal part of the syringe body which bears said needle, and a third portion which narrows from the second portion as far as the back of said housing.
Syringe needle protection devices of the afore-mentioned type have already been proposed.
For example, Patent EP 0 429 052 relates to a needle shielding assembly comprising, as is visible in FIG. 5, an elastic needle sheath similar to the elastic needle cap defined hereinabove.
However, this type of needle protection device presents a certain number of drawbacks.
The protection device for syringe needle forming the subject matter of the present invention is intended to be mounted on a hypodermic syringe for injecting a medicinal liquid into a patient.
Whether such hypodermic syringes are pre-filled or are to be filled by the hospital staff just before the injection is effected, these syringes must remain sterile until they are used.
For example, when the syringe is packaged when already filled with liquid, the following different steps are effected for preparing the syringe before it is packaged. In the first place, the body of the syringe, on the distal part of which is mounted a needle coated with a silicone coating, is washed. An elastic needle cap is then mounted on the needle to form an assembly which will subsequently be rendered sterile, preferably by passage in an autoclave.
After passage of the afore-mentioned assembly in an autoclave, the syringe is filled with the liquid which is intended for it and the syringe body is closed by the piston and plunger which complete the syringe before subsequent packaging thereof.
During passage in the autoclave, as the elastic needle cap is made of a material allowing the passage of gases (generally rubber), it is possible to make a pressure equilibrium between the outside of the elastic cap, i.e. the enclosure of the autoclave, and the interior of the elastic cap, i.e. the housing receiving the needle of the syringe.
During the cycle of sterilization in an autoclave, apart from an increase in the temperature in the enclosure of the autoclave, a considerable increase in the pressure is also conventionally effected after one or more partial vacuums in the enclosure (for example up to 2.3 bars). This maximum pressure is maintained for a certain time (pressure plateau) before a fresh partial vacuum is made in the enclosure of the autoclave. At the end of the cycle, the pressure is increased up to atmospheric pressure, while the temperature redescends progressively down to ambient temperature.
From the preceding explanations, it will be understood that, during the cycle of sterilization in an autoclave, there are fairly sudden pressure changes in the enclosure. For example, upon the sudden drop in pressure in the enclosure between the maximum pressure value and the partial vacuum, it happens that the pressure in the housing of the elastic cap cannot be balanced quickly enough, resulting in a momentary residual pressure in this housing which presents a value greater than that of the pressure prevailing in the enclosure.
In certain cases, particularly when the lateral wall of the elastic cap is not sufficiently resistant, the residual pressure present in the housing generates a deformation of this lateral wall which may lead to the relative displacement of the elastic cap with respect to the distal part of the syringe body on which the cap is mounted. Such displacement of the cap may even be so great that it may lead to a separation between the cap and the syringe body when the deformation undergone by the cap does not make it possible to retain the distal part of the syringe body in the housing.
In the case of the displacement between the cap and the syringe body, there may exist a rupture of tightness between the housing of the cap and the environment outside the cap, which induces a risk of loss of sterility in this housing, therefore of the needle. The loss of sterility is confirmed in the case of the separation between the cap and the syringe body.
Such displacement also induces a risk of leakage of liquid from the syringe, hence a dose of liquid in the syringe whose volume has decreased and a risk of contact with this liquid for the user, which may prove dangerous in the case of certain liquids used for examinations, particularly in medical imagery. Likewise, the contacting of the free end of the needle with the outside environment may generate physico-chemical reactions on the liquid, such as crystallization or coagulation, capable of degrading this liquid and of rendering the syringe unusable.
This risk of loss of sterility is all the greater in the case of the syringe body being made of glass, as the use of this material involves a range of dimensional tolerance much broader than in the case of a syringe made of plastics material.
The present invention has for its object to provide a protection device for syringe needle which does not present the drawbacks set forth hereinbefore, i.e. guaranteeing that the needle is maintained in a tightly closed sterile atmosphere until it is used, while conserving, and even improving, the facility of removal of the protection device by the user before the syringe is used.
This object is attained by a protection device for syringe needle of the type mentioned hereinabove, which is characterized in that the lateral wall of the cap is further provided with an annular bead disposed in said housing between said first and second portions of said housing, at least one slot extending longitudinally over said annular bead.
It will be understood that this annular bead makes it possible to retain the distal part of the syringe body in the housing of the cap, especially when there is a residual pressure inside this housing, the annular bead in that case constituting a mechanical retaining means preventing a relative displacement in longitudinal translation between the cap and the distal part of the syringe body. Said slot or slots facilitate the passage of the gases under pressure (in particular water vapor under pressure used during the passage in an autoclave and which effects sterilization) between the housing of the cap and the outside of the cap. In this way, a greater deformability of the annular bead in the housing is also obtained, which makes it possible to minimize the necessary tearing force when the cap and the syringe body are separated.
This annular bead is all the more efficient for retaining the distal part of the syringe body in the housing as this distal part is most often made in the form of a swell which may present a general shape of a ball or section of sphere. This swell presents, in its median part, a greater diameter than the part of revolution, often truncated, which is adjacent thereto. In this way, the annular bead is naturally housed in the annular depression formed on the distal part of the syringe body, between the swell forming the median part of the distal part and the part of revolution which is adjacent to the distal part.
According to an advantageous characteristic, said bead presents in longitudinal section the form of a half drop of water of which the widest part is turned in the direction of the proximal end of the cap. This shape is particularly adapted to retain the distal port of the syringe body in the housing during the passage in an autoclave while also allowing an easy separation between the cap and the body of the needle, this separation step preceding the use of the syringe.
The outer face of the lateral wall which surrounds the annular bead is preferably in the form of a frustum of a cone.
Furthermore, according to another embodiment of the invention, the protection device for syringe needle is provided also to comprise a rigid shell of general longitudinal cylindrical shape, of circular cross-section, presenting an open proximal end and an at least partially closed distal end, said shell comprising a longitudinal wall extending from said proximal end up to said distal end and a terminal wall located at its distal end, said shell being intended to surround and contain said elastic needle cap, and being provided with means for retaining said cap.
The main purpose of the additional use of a rigid shell surrounding the elastic cap is to protect all persons who successively manipulate the syringe from an accidental prick with the needle if the free end of the needle completely pierces the end wall of the elastic needle cap.
This rigid shell also presents the advantage of facilitating manipulation of the syringe needle protection device by the machines of the production and assembly lines, particularly when the protection device is mounted on the syringe.